Device for adjusting the tension of the upper thread in sewing machines



A. WMGNE FOR ADJUSTING THE TENSION OF Ehmm 6, E955 INES DEVICE THE UPPER THREAD IN SEWING MACH Filed April .14, 1955 m INVENTOR. A Pkg/7L 9mm fiffoyme s United States Patent DEVICE FOR ADJUSTING THE TENSION OF THE UPPER THREAD IN SEWING MACHINES Alessandro Pagni, Milan, Italy, assignor to Vittorio Necchi 'Societa per Azioni, Pavia, Itaiy Application April 14, 1953, Serial No. 348,635 Claims priority, application Italy April 21, 1952 4 Claims. (Cl. 242-150) The present invention relates to a thread tensioning device for sewing machines.

An object of the invention is to provide a construction which is compact requiring a minimum of space.

A further object is to provide a thread tensioning device wherein the graduation scales indicating the tension applied are easy to read.

A further object of the invention is to provide a construction wherein the pointer for the graduations is controlled indirectly and wherein such pointer is not directly dependent upon the revolutions of the control knob.

A still further object of the invention is to provide a construction wherein the thread tensioning device may be completely assembled prior to being mounted in the sewing machine.

With the above and other objects in view which will become apparent from the detailed description below and claimed in the claims, a preferred embodiment of the invention is disclosed in the drawings, wherein:

Fig. 1 is a perspective view of the assembled device;

Fig. 2 is a longitudinal cross-sectional view of the device shown in Fig. I mounted in a sewing machine;

Fig. 3 is a partial cross-sectional view of the construe tion shown in Fig. 2 illustrating a modification wherein a higher tension of the thread may be obtained making the device more suitable for the sewing of button holes, and

Fig. 4 is an exploded view of the device.

In the various views similar reference characters refer to like parts.

The control knob 1 for manual adjustment of the tension is provided with interior threading whereby it may be screwed upon the threaded end of the stud 2. A slidable drum 3 is provided with two helical grooves 3 spaced 180 from one another and also a longitudinally extending groove 3". A member 4 having an up bent end 4 is slidable in the groove 3" and the end 4 serves as the pointer for the reading of the graduations. A washer 5 is located Within the drum 3 and one end of the helical spring 8 bears against the same. Located within the spring 8 and concentric thereto is a second helical spring 6 having one end bearing against the retainer 7 abutting a shoulder provided upon the stud 2 and its other end bearing against the drum 3.

The other end of the spring 8 bears against a tension releasing disc 9 which in turn bears against the tensioning discs 10 and 11 between which the thread slides.

The stud 2 is axially bored and the threaded end receiving the knob 1 is diametrically milled.

The casing 12 enclosing the tensioning elements is provided with a slot 13 and a slot 14 which are axially displaced with relation to one another. Upon the casing 12 adjacent the slot 13 there is provided the graduations of the tensioning index as shown particularly in Figures 1 and 4 and such slot extends for about 40? of the circumference of the casing 12.

The slot 14 which extends for about 320 of the cirslides axially within 2,726,053 Patented Dec. 6, 1955 cumference of the casing 12 is provided for the introduction and extraction of the thread to the tensioning device.

Upon the casing 12 there are provided two openings 15 spaced at from one another in which there are located pins which will cooperate with the helical grooves 3. There is also provided a radially extending pin 16 and an opennig 16 therefore upon the: casing 12 which a bore provided upon the drum 3.

The casing 12 at the end to be inserted within the sewing machine 23 is provided with a reduced sleeve fixed to the stud 2 by means of the set screw 17. A helical spring 18 encircles such sleeve and has one end secured thereto while the other end 20 is free and is hook-shaped to guide the thread coming from the tensioning device. The compensating spring 18 is of conventional construction.

A casing 21 encloses the portion of the device which projects within the machine 23 and is secured to the sleeve of the casing 12 by means of a set screw 22.

When it is desired to sew button holes a ring 24 as shown in Fig. 3 and also at the right of Fig. 4 is inserted between the knob 1 and the drum 3. There are provided upon the ring 24 projections 25 which extend through the hole 26 provided in the drum 3 and the cut away portion 27 therein. The projections 25 push the washer 5 against the spring 8 so that a higher tensioning is attained than in normal use.

The operation of the tensioning device is as follows: Upon screwing the knob 1 upon the threaded portion of the stud 2 the drum 3 is displaced axially. The spring 8 is compressed and the drum .3 performs a slight rotation due to the pins of the casing 12 engaging in the grooves 3.

At the same time the member 4 slides longitudinally within the groove 3 and the pointer 4' moves with respect to the graduations upon the casing 12.

Upon unscrewing the knob 1 the spring 8 urges the drum 3 away from the machine and at the same time decreases the tension between the discs 10 and 11 until compression ceases when the spring 3 has assumed its free length. Then the spring 6 urges the drum 3 away from the machine a further distance thereby returning the pointer 4' to zero position.

The operation of the compensating spring 18 and the action of the disc 9 need not be described because their action is conventional use.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the form hereinbefore described and illustrated in the drawings being merely a preferred embodiment thereof.

What I claim is:

l. A tension device for sewing machines comprising a stud, a cup shaped casing coaxially fixed on said stud, a drum slidable within said casing having helical grooves therein, means upon said casing cooperating with said grooves, cooperating tension discs located within said casing, a spring located between said drum and said tension discs, said casing having a slot therein extending circumferentialiy thereof, graduations upon said casing adjacent said slot, a pointer projecting through said slot mounted slidably upon said drum and a knob threadedly engaged with said stud for displacing said drum axially against the action of said spring.

2. A tension device for sewing machines as set forth in claim 1 wherein an auxiliary member is interposed between said drum and said knob for increasing the tension exerted by said spring.

3. A tension device for sewing machines as set forth in claim 2 wherein the ring-shaped end of said auxiliary 3 member comprises projections for urging said spring a slight distance away from the point at which it acts upon said drum.

4. A tension device for sewing machines as set forth in claim 1 wherein a second spring is provided supplementing the action of said first spring and which cooperates with said stud.

1,534,264 Hanson Apr. 21, 1925 4 Chason Aug. Chason June Chason Sept. Robert July Parry et a1. Feb. Marsac Aug. Heizer May FOREIGN PATENTS Italy Apr. 

